Interpenetrating network nanoarchitectonics of antifouling poly(vinylidene fluoride) membranes for oil-water separation.

Poly(vinylidene fluoride) (PVDF) membranes are a commonly used cheap material and have been widely used in wastewater treatment. In this study, a simple strategy was proposed to construct PVDF-g-PEG membranes with an interpenetrating network structure by simulating plant roots for the treatment of oil/water emulsion. Meanwhile, the hydrophilicity, antifouling, and mechanical properties of the membrane were improved. A series of chemical and physical characterization methods were used to verify the successful formation of a PVDF-g-PEG layer on the membrane surface. The effects of graft modifier content on the crystallization behavior, microstructure, and membrane permeability were studied. When the optimized membrane (m-PVDF-2) was applied to the treatment of oily wastewater, its separation performance was significantly better than that of the blank PVDF membrane, and the oil removal rate was over 99.3%. BSA and oil contamination were nearly reversible, and excellent oil resistance to high-viscosity oil was also observed. The method reported in this article is a one-step, simple method for constructing hydrophilic and oil-resistant PVDF membranes without any intermediate additives and harmful or costly catalysts. They can be used as an ideal material for preparing efficient oil-water separation membranes.

Boosting the anode performance of microbial fuel cells with a bacteria-derived biological iron oxide/carbon nanocomposite catalyst.

Modifying the electrodes of microbial fuel cells (MFCs) with iron oxides can improve the bacterial attachment performances and electrocatalytic activities for energy conversion, which is of significance in the fabrication of MFCs. However, the conventional modification methods usually result in the aggregation of iron sites, producing the electrodes of poor qualities. Herein, we report a novel method for the modification of electrochemical electrodes to boost the anode performance of MFC. The Shewanella precursor adhered on carbon felt electrode was directly carbonized to form a bacteria-derived biological iron oxide/carbon (Bio-FeOx/C) nanocomposite catalyst. The large spatial separation between the bacteria, as well as those between the iron containing proteins in the bacteria, deliver a highly dispersed Bio-FeOx/C nanocomposite with good electrocatalytic activities. The excellent microbial attachment performance and electron transfer rate of the Bio-FeOx/C modified electrode significantly promote the transfer of produced electrons between bacteria and electrode. Accordingly, the MFC with the Bio-FeOx/C electrode exhibits the maximum power density of 797.0 mW m-2, much higher than that obtained with the conventional carbon felt anode (226.1 mW m-2). Our works have paved a new avenue to the conversion of the natural bacterial precursors into active iron oxide nanoparticles as the anode catalyst of MFCs. The high catalytic activity of the prepared Bio-FeOx endows it great application potentials in the construction of high-performance electrodes.

Molecular Characterization of Organics Removed by a Covalently Bound Inorganic-Organic Hybrid Coagulant for Advanced Treatment of Municipal Sewage.

Coagulation is an important process to remove organics from water. The molecular composition and structure of organic matter influence water quality in many ways, and the lack of information regarding the organics removed by different coagulants makes it challenging to optimize coagulation processes and ensure reclaimed water safety. In this paper, we investigated coagulation of secondary biological effluent from a municipal sewage treatment plant with different coagulants. We emphasized investigation of organics removal characteristics at the molecular level using Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with electrospray ionization (ESI). We found that conventional coagulants can only partially remove condensed polycyclic aromatics and polyphenols with low H/C (H/C < 0.7) and highly unsaturated and phenolic compounds and aliphatic compounds with high O/C (O/C > 0.6). A new coagulant, CBHyC, had better removal efficiencies for all organics with different element compositions and molecular structures, especially organics that are resistant to conventional coagulants such as highly unsaturated and phenolic compounds and aliphatic compounds located in 0.3 < O/C < 0.8 and 1.0 < H/C < 2.0 regions and sulfur-containing compounds with higher O/C (e.g., anionic surfactants and their metabolites or coproducts). This study provides molecular insights into the organics removed by different coagulants and provides data supporting the possible optimization of advanced wastewater treatment processes.

Arsenite removal from aqueous solution by a microbial fuel cell-zerovalent iron hybrid process.

Conventional zerovalent iron (ZVI) technology has low arsenic removal efficiency because of the slow ZVI corrosion rate. In this study, microbial fuel cell (MFC)-zerovalent iron (MFC-ZVI) hybrid process has been constructed and used to remove arsenite (As(III)) from aqueous solutions. Our results indicate that the ZVI corrosion directly utilizes the low-voltage electricity generated by MFC in the hybrid process and both the ZVI corrosion rate and arsenic removal efficiency are therefore substantially increased. The resultant water qualities are compliant with the recommended standards of EPA and WHO. Compared to the ZVI process alone, the H2O2 generation rate and output are dramatically improved in MFC-ZVI hybrid process. Strong oxidants derived from H2O2 can rapidly oxidize As(III) into arsenate (As(V)), which helps to improve the As(III) removal efficiency. The distribution analysis of As and Fe indicates that the As/Fe molar ratio of the flocs in solution is much higher in the MFC-ZVI hybrid process. This phenomenon results from the different arsenic species and hydrous ferric oxides species in these two processes. In addition, the electrosorption effect in the MFC-ZVI hybrid process also contributed to the arsenic removal by concentrating As(V) in the vicinity of the iron electrode.

[Species distribution and coagulation behavior of covalent bonded aluminum-silicon hybrid flocculants].

Covalent bonded aluminum-silicon hybrid flocculants were synthesized by employing tetraethylorthosilicate (TEOS) and two silane coupling agents [diethoxydimethylsilane (DEDMS), gamma-aminopropylmethyldiethoxysilane (APDES)] as silicon sources, respectively. The distribution of Al species was investigated by 27Al NMR method and the coagulation behavior was evaluated by treating synthetic water containing humic acid. The results of 27Al NMR show that silicon source, Si/Al molar ratio and basicity (B) exhibit effect on the Al species distribution. In the products with APDES as silicon source, the highest content of Al13 was obtained and its amount increases with the rise of Si/Al molar ratio. The effect of B value on the Al species is similar for the three sets of flocculants. The content of monomeric species decreases with the rise of B value. At Si/Al = 0.4, there are no Al13 observed throughout the B value range in the products with TEOS as silicon source. Al13 starts to appear at a higher B value of 1.5 for the products with DEDMS as silicon source and a lower B value of 0.5 for that with APDES as silicon source, respectively. The coagulation results show that, in acidic conditions, the best dosage range of the flocculants with APDES as silicon source is the widest of the three, resulting in the best coagulation efficiency. In alkaline conditions, the coagulation efficiency of the products with TEOS as silicon source is slightly better than the other two.

Covalently bound organic silicate aluminum hybrid coagulants: preparation, characterization, and coagulation behavior.

Covalently bound organic silicate aluminum hybrid coagulants were synthesized by employing two silane coupling agents [diethoxydimethylsilane (DEDMS), gamma-aminopropylmethyldiethoxysilane (APDES)] as silicon sources. An additional coagulant was synthesized using anothersilane-tetraethylorthosilicate (TEOS) for comparison. Both the coagulant with DEDMS and that with APDES as the silicon source were shown to be covalently bound by infrared (IR) analysis. All three hybrid coagulants were characterized by pH, zeta potential, Al species distribution, and transmission electron microscopy (TEM) analysis. The results indicated that the silicon source played a significant role in aspects of the chemical and physical structure, Al species distribution, and electrochemistry characteristics. Specifically, the coagulant with APDES as the silicon source featured the highest zeta potential value, the highest content of Al13, and reticulated aggregate. The coagulation behaviors of the three hybrid coagulants were also investigated by treating synthetic water containing humic acid (HA). The hybrid coagulant with APDES as the silicon source exhibited the best coagulation behavior in terms of HA removal and turbidity removal, due to the combination of the zeta potential, Al species distribution, and organic functional groups.

Study on treatment of coking wastewater by biofilm reactors combined with zero-valent iron process.

Experiments were conducted to investigate the behavior of the integrated system with biofilm reactors and zero-valent iron (ZVI) process for coking wastewater treatment. Particular attention was paid to the performance of the integrated system for removal of organic and inorganic nitrogen compounds. Maximal removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH(3)-N) and total inorganic nitrogen (TIN) were up to 96.1, 99.2 and 92.3%, respectively. Moreover, it was found that some phenolic compounds were effectively removed. The refractory organic compounds were primarily removed in ZVI process of the integrated system. These compounds, with molecular weights either ranged 10,000-30,000 Da or 0-2000 Da, were mainly the humic acid (HA) and hydrophilic (HyI) compounds. Oxidation-reduction and coagulation were the main removal mechanisms in ZVI process, which could enhance the biodegradability of the system effluent. Furthermore, the integrated system showed a rapid recovery performance against the sudden loading shock and remained high efficiencies for pollutants removal. Overall, the integrated system was proved feasible for coking wastewater treatment in practical applications.

[Al species distribution of organic silicate aluminum hybrid flocculants by Al-ferron complexation timed spectrophotometric method].

New types of organic silicate aluminum hybrid flocculants were prepared by employing Tetraethylorthosilicat (TEOS), Diethoxydimethylsilane (DEDMS), gamma-Aminopropylmethyldiethoxysilane (APDES) as silicon source. The Al species distribution in these new products was investigated by Al-Ferron complexation timed spectrophotometric method. The results show that silicon source, basicity (B) and Si/Al molar ratio have effect on the Al species distribution. Among them, basicity has greater effect, three sets of products have similar characteristics. The content of Al(a) declines with the rise of B value, while the contents of Al(b) and Al(c) increase. Al(c) is the dominant Al species in the products with TEOS as silicon source. DEDMS has little contribution to the distribution of Al species. In the products with APDES as silicon source, Al(c) is the dominant Al species while the content increases with the rise of Si/Al molar ratio.

Advanced treatment of coking wastewater by coagulation and zero-valent iron processes.

Advanced treatment of coking wastewater was investigated experimentally with coagulation and zero-valent iron (ZVI) processes. Particular attention was paid to the effect of dosage and pH on the removal of chemical oxygen demand (COD) in the two processes. The results showed that ZVI was more effective than coagulation for advanced treatment of coking wastewater. The jar tests revealed that maximal COD removal efficiency of 27.5-31.8% could be achieved under the optimal condition of coagulation, i.e. 400mg/L of Fe(2)(SO(4))3 as coagulant at pH 3.0-5.0. On the other hand, the COD removal efficiency could be up to 43.6% under the idealized condition of ZVI upon 10 g/L active carbon and 30 g/L iron being dosed at pH 4.0. The mechanisms for COD removal in ZVI were dominated by coagulation, precipitation and oxidation-reduction. ZVI would also enhance the biodegradability of effluent by increasing BOD5/COD from 0.07 to 0.53. Moreover, some ester compounds could be produced in the reaction. Although ZVI was found more efficient than coagulation in eliminating low molecular weight (<2000 Da) compounds in the wastewater, there were still a few residual contaminants which could hardly be eliminated by either of the process.